How to clone existing KVM virtual machine images on Linux

I

wanted to clone my Debian or Ubuntu Linux KVM VM for testing purpose. How do I clone existing virtual machine images under KVM?

 

You can use a simple command named virt-clone. It is a command line utility for cloning existing virtual machine images using the “libvirt” hypervisor management library. It will copy the disk images of any existing virtual machine, and define a new guest with an identical virtual hardware configuration. Elements which require uniqueness will be updated to avoid a clash between old and new guests.

How to clone your VM and spawn new instances in KVM

The syntax is

# virt-clone –original {Domain-Vm-Name-Here} –auto-clone

 

OR

# virt-clone –original {Domain-Vm-Name-Here} \

–name {New-Domain-Vm-Name-Here}

Examples

First VM/domain with devices to clone must be paused or shutoff. To gracefully shutdown a domain named ubuntu-box1, run:

$ sudo virsh shutdown ubuntu-box1

 

OR you can paused it as follows:

$ sudo virsh suspend ubuntu-box1

$ virsh list

 

Sample outputs:

Domain ubuntu-box1 suspended

 

Id    Name                           State

---

1     freebsd                        running

5     ubuntu-box1                    paused

Let us generate a new guest name, and paths for new storage automatically for a vm called ubuntu-box1

$ sudo virt-clone –original ubuntu-box1 –auto-clone

 

Sample outputs:

WARNING  Setting the graphics device port to autoport, in order to avoid conflicting.

Allocating  ubuntu-box-1-clone.qcow2                                                               |  40 GB  00:00:04

 

Clone  ubuntu-box1-clone  created successfully.

The above command cloned the guest called “demo” on the default connection, auto generating a new name called ubuntu-box1-clone and disk clone path. You can start or resume original domain:

$ sudo virsh start ubuntu-box1

 

OR

$ sudo virsh resume ubuntu-box1

 

Next, start ubuntu-box1-clone, enter:

$ sudo virsh start ubuntu-box1-clone

 

Verify it:

$ virsh list

 

My dhcpd server gave 192.168.2.147 IP address to ubuntu-box1-clone VM, run:

$ ping -c2 192.168.2.147

 

Finally, ssh into the box:

$ ssh vivek@192.168.2.147

 

Sample sessions:

Fig.01 virt-clone command cloned existing virtual machine images

 

Please note, virt-clone does not change anything inside the guest OS, it only duplicates disks and does host side changes. So things like changing passwords, changing static IP address, ssh-keys, hostnames etc are outside the scope of this tool. Once login using to cloned VM using ssh, you can change those:

$ ssh vivek@192.168.2.147

$ sudo -s

# echo  ubuntu-box1-clone  > /etc/hostname

# sed -i  s/ubuntu-box1/ubuntu-box1-clone/g  /etc/hosts

# reboot

# /bin/rm -v /etc/ssh/ssh_host_*

# dpkg-reconfigure openssh-server

# passwd vivek

 

You can use virt-sysprep instead of virt-clone if you need to clone the VM and make/reset anything inside the guest OS.